Peptidoglycan deacetylation in Helicobacter pylori contributes to bacterial survival by mitigating host immune responses.

An oxidative stress-induced enzyme, peptidoglycan deacetylase (PgdA), in the human gastric pathogen Helicobacter pylori was previously identified and characterized. In this study, we constructed H. pylori pgdA mutants in two mouse-adapted strains, X47 and B128, to investigate the role of PgdA in vivo (to determine the mutants' abilities to colonize mice and to induce an immune response). H. pylori pgdA mutant cells showed increased sensitivity to lysozyme compared to the sensitivities of the parent strains. We demonstrated that the expression of PgdA was significantly induced (3.5-fold) when H. pylori cells were in contact with macrophages, similar to the effect observed with oxidative stress as the environmental inducer. Using a mouse infection model, we first examined the mouse colonization ability of an H. pylori pgdA mutant in X47, a strain deficient in the major pathway (cag pathogenicity island [PAI] encoded) for delivery of peptidoglycan into host cells. No animal colonization difference between the wild type and the mutant was observed 3 weeks after inoculation. However, the pgdA mutant showed a significantly attenuated ability to colonize mouse stomachs (9-fold-lower bacterial load) at 9 weeks postinoculation. With the cag PAI-positive strain B128, a significant colonization difference between the wild type and the pgdA mutant was observed at 3 weeks postinoculation (1.32 × 10(4) versus 1.85 × 10(3) CFU/gram of stomach). To monitor the immune responses elicited by H. pylori in the mouse infection model, we determined the concentrations of cytokines present in mouse sera. In the mice infected with the pgdA mutant strain, we observed a highly significant increase in the level of MIP-2. In addition, significant increases in interleukin-10 and tumor necrosis factor alpha in the pgdA mutant-infected mice compared to the levels in the wild-type H. pylori-infected mice were also observed. These results indicated that H. pylori peptidoglycan deacetylation is an important mechanism for mitigating host immune detection; this likely contributes to pathogen persistence.

Preoperative platelet inhibition with eptifibatide during coronary artery bypass grafting with cardiopulmonary bypass.

Platelet glycoprotein IIb-IIIa antagonists reduce cardiac events in acute coronary syndromes (ACSs), but their use is limited during coronary artery bypass grafting (CABG) because of bleeding concerns. Patients with ACS, however, are at increased risk for cardiac events after CABG. The use of short-acting glycoprotein IIbIIIa inhibitor eptifibatide in patients with ACS undergoing CABG was investigated. Fifteen patients with ACS and undergoing CABG with cardiopulmonary bypass were enrolled. One withdrew before surgery. Patients received heparin and eptifibatide preoperatively. Eptifibatide concentration and receptor occupancy (RO) at termination of infusion were similar in the two groups. Immediately before surgery, eptifibatide levels in the 2-hour group were twice that in the 4-hour group, and platelet RO was higher. Cessation of eptifibatide 4 hours before surgery results in less bleeding and transfusions than 2 hours before surgery. The optimal balance between bleeding and platelet inhibition is approximately 60% platelet RO. Further investigation of upstream therapy should target this threshold.

Preemptive use of bivalirudin for urgent on-pump coronary artery bypass grafting in patients with potential heparin-induced thrombocytopenia.

PURPOSE: The use of heparin in patients with heparin-induced thrombocytopenia (HIT) may result in severe complications or death. The diagnosis of HIT is frequently uncertain, however. Alternative anticoagulants in at-risk patients undergoing cardiac surgery with cardiopulmonary bypass remain problematic. The novel short-acting, direct-thrombin inhibitor bivalirudin is the only alternative to heparin/protamine being used in elective non-HIT patients during CPB. DESCRIPTION: Four patients with severe thrombocytopenia after heparin exposure and suspected acute HIT underwent on-pump coronary artery bypass grafting surgery with preemptive use of bivalirudin. A continuous bivalirudin infusion was used during cardiopulmonary bypass, and activated clotting times were used to monitor anticoagulation. EVALUATION: Anticoagulation with bivalirudin during cardiopulmonary bypass was effective and uncomplicated. Duration of operation was not prolonged, and perioperative blood loss and transfusion rates were acceptable. Activated clotting times were helpful for monitoring anticoagulation in these patients. CONCLUSIONS: These data provide further evidence of the feasibility of bivalirudin for anticoagulation during on-pump coronary artery bypass graft surgery in urgent clinical situations.